| A | B |
|---|
| Midpoint | The point of that line segment that divides the segment into two congruent segments |
| Bisector of a Line Segment | A line or subset of a line that intersects the segment at its midpoint |
| Ray | A part of a line that consists of a point on the line, called an endpoint, and all points on one side of the endpoint |
| Opposite Rays | Two rays of the same line with a common endpoint and extending in opposite directions |
| Collinear Points | A set of points all of which lie on the same straight line |
| Line segment | A set of points consisting of two points on a line, called endpoints, and all points in between them |
| Angle | A set of points that is a union of two rays having the same endpoint |
| Right Angle | An angle whose degree measure is 90 |
| Straight Angle | An angle whose degree measure is 180 |
| Acute Angle | An angle whose degree measure is greater than 0 and less than 90 |
| Obtuse Angle | An angle whose degree measure is greater than 90 and less than 180 |
| Angle Bisector | A ray whose endpoint is the vertex of the angle and divides the angle into two congruent angles |
| Adjacent Angles | Two angles in the same plane that have a common side and vertex but do not have any interior points in common |
| Vertical Angles | Two angles in which the sides of one angle are opposite rays to the sides of the second angle |
| Complementary Angles | Two angles whose measure sum 90 |
| Supplementary Angles | Two angles whose measure sum to 180 |
| Linear Pair | Two angles that are adjacent and supplementary |
| Perpendicular Lines | Two lines that intersect to form right angles |
| Perpendicular Bisector | A line or a portion of a line that intersects the line segment to form right angles and bisects the line segment at its midpoint |
| Scalene Triangle | A triangle that has no congruent sides |
| Isosceles Triangle | A triangle that has two congruent sides |
| Equilateral Triangle | A triangle that has three congruent sides |
| Acute Triangle | A triangle that has three acute angles |
| Equilateral Triangle | A triangle that has three congruent angles |
| Right Triangle | A triangle that has a right angle |
| Obtuse Triangle | A triangle that has an obtuse angle |
